Bradford were a threat in wide areas but Millwall were relatively comfortable until Kyel Reid glided past Carlos Edwards and picked out Jamie Proctor in the box just before the break. Jordan Archer did well to spread himself to save the first shot but Proctor fired the rebound into the roof of the net for the equaliser.

Bantams boss Phil Parkinson thought his side should have had a penalty with just under 20 minutes left when substitute Tom Thorpe went down under Mark Beevers’ challenge. Any contact, though, appeared to be outside the box.

Parkinson brought on centre-forward Steven Davies for defender Nathan Clarke in the second half but Bradford never really tested Archer as Millwall comfortably kept their advantage.

The result made it nine games unbeaten at home for Millwall but Harris felt the crucial work had been done in the first leg at Valley Parade last Sunday, particularly Gregory's equalising strike so soon after Tony McMahon's opener.

“I’m proud of my players, two legs against Bradford were always going to be challenging and tough,” Harris said. “I think if you broke the tie down to four halves of football the first goal at Valley Parade possibly won us the tie, getting back into it so quickly.

“My praise is for my players, the character shown through adversity, the five-minute spells we’ve had to come through, relying on each other and being solid in our shape.

“And then we had moments of quality, we’ve been top drawer over the two legs.”

Gregory’s goal was his 27th of the season, but Harris felt the defensive resilience was key over both games.

“Steve and Lee got a lot of plaudits in the first game and will do again and rightly so for the goal. I think (the defensive display) was the biggest achievement over the two legs.

“And again for us tonight the one real bit of quality we had the ball ends up in the back of the net. Fortunately we had three bits of quality at the weekend and scored three goals. The two up front have been talismans along with Aiden O’Brien who has scored 13 goals.

“To be successful you need players that are scoring goals.”

Parkinson also felt referee Tim Robinson was influenced by the home crowd, but Harris dismissed that suggestion.

“I thought the atmosphere was electric, it was hostile, it was a really top Millwall crowd,” Harris said. “You want a Millwall crowd to influence what happens on the pitch, of course you do. That’s what’s made us so good over the years, a big part of it.

“I thought the fans were brilliant, they showed tonight the disappointment with the difficult times they’ve had over the years in the Championship. They’ve missed (the occasions) and they want the good times.

“I think only the referee will know if he was influenced by the crowd but I don’t think he got many 50/50 decisions wrong.”